THE ROLE OF VITAMINS IN THE PATHOGENESIS AND TREATMENT OF HYPERHOMOCYST(E)INAEMIA

The relation between vitamin nutritional status and circulating plasma homocyst(e)ine concentrations is reviewed. Several studies have shown that plasma concentrations of folate, vitamin B-12 and pyridoxal 5'-p hosphate are inversely associated with plasma total homocyst(e)ine con centrations. Of the three vitamins mentioned above, folate is the most powerful homocyst(e)ine lowering agent and a daily supplement of 0.65 mg/day is sufficient to normalize moderate hyperhomocyst(e)inaemia in most individuals with normal renal function. In patients with severe renal failure, high doses of folate are required to treat hyperhomocys t(e)inaemia. Folic acid is ineffective in reducing plasma total homocy st(e)ine concentrations in patients with a vitamin B-12 deficiency. Vi tamin B-6 supplementation has no effect on fasting plasma total homocy st(e)ine concentrations, but attenuates the post-methionine load plasm a homocyst(e)ine peak. At least one report has shown that some individ uals appear to be unable to maintain plasma total homocyst(e)ine conce ntrations in the normal reference range by a dietary intake of folic a cid only. Long-term vitamin supplementation may be indicated in these individuals. However, the clinical benefit of vitamin supplementation has not yet been demonstrated and controlled trials are urgently requi red.